<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>过滤器加载器</title>
</head>
<body>
<div>div1</div>
<div id="div2">div2</div>
<div>div3</div>
<div>div4</div>
</body>
<script src="js/jquery-3.3.1.min.js"></script>
<script>
    let div1  =$("div:first");
    alert("首元素加载器"+div1.html())

    let div4 = $("div:last");
    alert("尾元素加载器" +div4.html())

    let divs1 = $("div:not(#div2)")
    alert("非元素加载器"+divs1.length)

    let divs2 =$("div:even")
    alert("偶数加载器"+divs2.length)

    let divs3=$("div:odd")
    alert("奇数加载器"+divs3.length)

    let divs4=$("div:gt(1)")
    alert("大于索引加载器:"+divs4.length)

    let divs =$("div:lt(3)")
    alert("小于索引加载器"+divs.length)

</script>
</html>